1. Field of the Invention
The present invention relates to a disk scanning type confocal microscope, which performs confocal observation with respect to a sample.
2. Description of the Related Art
FIG. 13 shows a structure of a conventional example of a disk scanning type confocal microscope. In FIG. 13, light from a light source 1 such as a mercury light source is transmitted through a lens 2 and an excitation filter 3, reflected by a dichroic mirror 4, and then applied onto a rotary disk 5, which is located at an intermediate image position conjugate with a sample surface.
The rotary disk 5 has confocal openings, and is rotated at a fixed speed by a motor 6. The light transmitted though the confocal openings of the rotary disk 5 is applied onto a sample 8 through an objective lens 7. Fluorescence emitted from the sample 8 is likewise transmitted through the objective lens 7 and the confocal openings of the rotary disk 5, and focused onto a CCD camera 11 by an image formation lens 10 through the dichroic mirror 4 and an absorption filter 9. At this time, since only the light transmitted through the confocal openings is focused onto the CCD camera, a confocal image, which is sharp-edged in a cross-sectional direction, is obtained on a monitor 12.
Further, the rotary disk can be generally arbitrarily inserted into/removed from an optical path by moving means, not shown, and confocal observation and normal observation are switched in accordance with insertion/removal of the rotary disk.
The confocal effect depends on a ratio of a light beam diameter and an opening diameter. Since the light beam diameter is represented by 1.22 λ/NA (λ: light source wavelength, NA: numerical aperture), the confocal effect depends on NA of the objective lens. Therefore, when the objective lens is changed to one with a different NA with respect to the same confocal openings, the confocal effect is also changed.
For this reason, in the confocal microscope, the confocal opening must have a size matching with (i.e., suitable for) of the NA (numerical aperture) of the objective lens to be used for the preferable observation, i.e., in order to obtain the same confocal image irrespective of the NA of the objective lens. Therefore, in the disk scanning type confocal microscope, the rotary disk has the confocal openings whose size is appropriate for the NA (numerical aperture) of the objective lens to be used.
Jpn. UM Appln. KOKAI Publication No. 5-75719 discloses a structure in which the confocal effect is changed by varying the NA of light entering the confocal openings on a rotary disk by a relay lens.
Jpn. Pat. Appln. KOKAI Publication No. 2000-275542 discloses a structure in which a disk has confocal opening patterns, which respectively correspond to objective lenses and arranged in a circumferential direction on the disk, and a CCD camera is caused to perform imaging in synchronization at the time of scanning in each area.
It is to be noted that the description has been given as to the disk scanning type confocal microscope for fluorescence observation as the prior art, but the same description can be applied to a disk scanning type confocal microscope adopting a polarization mode, which is constituted by substituting a polarizing beam splitter for three components, i.e., the excitation filter 3, the dichroic mirror 4, and the absorption filter 9, and arranging a quarter wave plate between the polarizing beam splitter and the objective lens 7.